Review Question - QID 221324

This patient with severe, crushing, sub-sternal chest pain, and ST-segment elevations on ECG most likely has an acute myocardial infarction. Nitroglycerin would lead to an immediate decrease in pain without altering mortality and this medication acts via venodilation to reduce cardiac preload and thus myocardial oxygen demand.

Acute myocardial infarction is a life-threatening reason for presentation to the emergency department. When an acute myocardial infarction is suspected, several therapies are started. The most important of these is aspirin which is an irreversible cyclooxygenase inhibitor that is given immediately if acute myocardial infarction is on the differential. Other therapies include nitroglycerin for pain unless a right-sided myocardial infarction is suspected, heparin, antiplatelet therapy such as clopidogrel, statins, and beta-blockers (upon discharge). The therapies that reduce mortality are aspirin, heparin, anti-platelet therapy, and beta-blockers. Nitroglycerin decreases pain without changing mortality by decreasing preload.

Figtree et al. studied mortality in STEMI patients without standard modifiable risk factors. They discuss how patients without standard modifiable risk factors were less likely to receive optimal medical therapy and more likely to have 30-day post-MI mortality. They recommend adherence to evidence-based pharmacotherapy at discharge to attenuate this increased risk.

Figure/Illustration A is an ECG demonstrating ST elevation in the anterolateral leads (red circle). This finding is consistent with a myocardial infarction.

Incorrect Answers:
Answer 1: Blockade of beta-adrenergic receptors describes the mechanism of action of the beta-blocker class of drugs. In the outpatient setting, beta-blockers are given to all patients with acute myocardial infarction unless contraindicated, as they reduce mortality, but they do not reduce pain.

Answer 2: Blockade of the enzyme HMG-CoA reductase describes the mechanism of action of statins. Statins are given to all patients with acute myocardial infarction and reduce mortality, but they do not reduce pain.

Answer 3: An increase in arterial partial pressure of oxygen is achieved in myocardial infarction patients with high-flow oxygen therapy. This therapy is only given if patients are hypoxic.

Answer 4: Irreversible inhibition of cyclooxygenase-1 describes the mechanism of action of aspirin. Aspirin reduces mortality in acute myocardial infarction.

Bullet Summary:
Nitroglycerin reduces chest pain rapidly in acute myocardial infarction by venodilation, which reduces cardiac preload and subsequently myocardial oxygen demand.